Measles virus (MV), a member of the paramyxovirus family, remains one of the ten most lethal human pathogens despite the existence of a live-attenuated vaccine. The virus is endemic in Africa, Asia and parts of Europe, and cases are reported annually in the US. No therapy is available for management of severe cases of measles or rapid control of local outbreaks. It is therefore the long-term objective of this project to develop novel inhibitors of MV. Towards this goal multiple assays have been established in pilot studies and a research plan with three specific aims will be implemented. The first specific aim provides a robust assay to the MLSCN for hit identification through high throughput screening (HTS). A cell-based automated assay has been established that employs a fluorescent MV reporter stably expressing green fluorescent protein as additional transcription unit. Assay evaluation has revealed favorable z'-values of 0.8 and a pilot screen of a 34,000 compound in- house library at Emory has yielded amongst others a promising new inhibitor class, providing proof-of-concept for the approach. The second specific aim backs up the automated hit discovery with three independent manual assays that quantify suppression of virus-induced cytopathicity and reduction of virus yields in the presence of compound, and determine inherent compound cytotoxicity. Collectively, these assays allow hit confirmation, calculation of active concentrations, and assessment of compound selectivity. The third specific aim determines the target specificity of potent hits towards MV in comparison with other members of the paramyxovirus family, and subjects selected candidates to an initial characterization of the mechanism of antiviral activity. Candidate probes with high biologic activity towards MV will be subjected to testing against closely related canine distemper virus and distantly related human parainfluenza virus type 2. In individual assays, the effect of selected compounds on receptor binding, membrane fusion, and viral gene expression and genome replication will then be examined. Combined, this screening exercise will enable us to identify the most promising small molecule probes that merit future biochemical characterization of docking modes, further in vitro optimization through generation of quantitative structure-activity relationships and pharmacophore extraction, and in vivo toxicity and efficacy testing using the cotton rat small animal model for MV infection. Collectively, paramyxoviruses are responsible for significant morbidity and mortality worldwide. Measles virus (MV) alone, a member of this virus family, accounts for approximately 500,000 deaths annually, placing it among the most lethal human pathogens despite the existence of a vaccine. This is partially due to the exceptionally high infectivity of MV and the fact that no therapy is available for management of severe cases of measles or rapid control of local outbreaks. The high-throughput screening-based identification of novel biological probes that interfere with MV replication and spread, and the further development of applicable drugs based on these probes is therefore the ultimate objective of this project. [unreadable] [unreadable] [unreadable]